The invention relates to a method for the partial-area-specific fertilization of plants in which, by means of sensors, the chlorophyll content of the plants is determined by optical reflection measurement in the visible and near-infrared spectral ranges, the chlorophyll content is registered and from it the amount of nutrients required for the plants is determined and the corresponding fertilizer quantity to be applied is controlled by a computer.
The invention relates further to an apparatus for the partial-area-specific fertilization of plants having a displaceable carrier, especially a vehicle, which is equipped with an evaluating unit, a dispenser on the rear of the carrier for variable distribution of the fertilizer and a light waveguide affixed to the carrier and directed onto the plant stock in the direction of travel of the advancing carrier and connected with a spectrometer for spectral analysis of the reflected radiation and which supplies the reflection data for evaluation to the evaluation unit.
It is known to determine the nutrient state of plants taking into consideration their chlorophyll contents (xe2x80x9cPrecisexe2x80x9d brochure of Hydro Agri, 1997). The chlorophyll content is customarily ascertained by means of optical reflection sensors as has been basically described in U.S. Pat. No. 4,986,665.
The spectral reflection data recovered is obtained in all known solutions operating with natural light hitherto always in a vertical incidence position from above. Inclined pick-up angles result in an influence upon the reflection spectra by the solar azimuth angle and thus a falsification of the measurement results. Defined measurement conditions are thus very difficult to maintain.
The maintenance of the vertical incidence position requires, in addition, extraordinarily expensive structures for mounting the light guides on the displaceable carrier so as to pass the light guides with a sufficient spacing outside of the shadow region of the carrier above the plant stock. So that a sufficiently large area of the stock can be sensed, a plurality of expensive light guides are affixed on the carrier and are attached to bars articulated to swing out in the width direction.
Because of the outwardly swung bars, the maneuverability of the carrier/vehicle on the field is limited and there is a danger of running into obstructions.
In this state of the art the invention sets forth the object of so improving a method and device of the type described at the outset that in spite of an inclined measurement, the effect of the solar azimuth remains excluded and the robustness and compactness of the measurement system is increased while at the same time the vehicle or carrier can be serviced more simply.
These objects are achieved by a method of the kind set forth at the outset with the characterizing features of claim 1 and by a device with the characterizing features of claims 5 and 9. Advantageous configurations of the method and the device are deducible from the dependent claims.
The method of the invention enables the chlorophyll content of the plants to be determined as a measure of their nutrient state in an optical reflection inclined scan without an effect of the solar azimuth angle on the measurement results and thus the usable to noise signal ratio is reduced [sic].
The device of the invention for carrying out the method has the advantage of a compact and robust construction with simultaneously simpler serviceability.
With all of these features it is possible to better achieve the solution according to the invention of the complex requirements of a partial-area-specific fertilization with high efficiency and precision.